Rui,
Your response nearly answered a similar question of mine except that I also
have ecdfs of different lengths.
Do you know how I can adjust x <- seq(min(loga, logb), max(loga, logb),
length.out=length(loga))
to account for this? It must be in length.out() but I'm unsure how to
proceed.
Any advice is much appreciated.
-L
Rui Barradas wrote
Hello,
Try the following.
(i've changed the color of the first ecdf.)
loga <- log10(a+1) # do this
logb <- log10(b+1) # only once
f.a <- ecdf(loga)
f.b <- ecdf(logb)
# (2) max distance D
x <- seq(min(loga, logb), max(loga, logb), length.out=length(loga))
x0 <- x[which( abs(f.a(x) - f.b(x)) == max(abs(f.a(x) - f.b(x))) )]
y0 <- f.a(x0)
y1 <- f.b(x0)
plot(f.a, verticals=TRUE, do.points=FALSE, col="blue")
plot(f.b, verticals=TRUE, do.points=FALSE, col="green", add=TRUE)
## alternatine, use standard R plot of ecdf
#plot(f.a, col="blue")
#lines(f.b, col="green")
points(c(x0, x0), c(y0, y1), pch=16, col="red")
segments(x0, y0, x0, y1, col="red", lty="dotted")
## alternative, down to x axis
#segments(x0, 0, x0, y1, col="red", lty="dotted")
Hope this helps,
Rui Barradas
maxbre wrote
Hi all,
given this example
#start
a<-c(0,70,50,100,70,650,1300,6900,1780,4930,1120,700,190,940,
760,100,300,36270,5610,249680,1760,4040,164890,17230,75140,1870,22380,5890,2430)
length(a)
b<-c(0,0,10,30,50,440,1000,140,70,90,60,60,20,90,180,30,90,
3220,490,20790,290,740,5350,940,3910,0,640,850,260)
length(b)
out<-ks.test(log10(a+1),log10(b+1))
# max distance D
out$statistic
f.a<-ecdf(log10(a+1))
f.b<-ecdf(log10(b+1))
plot(f.a, verticals=TRUE, do.points=FALSE, col="red")
plot(f.b, verticals=TRUE, do.points=FALSE, col="green", add=TRUE)
#inverse of ecdf a
x.a<-get("x", environment(f.a))
y.a<-get("y", environment(f.a))
# inverse of ecdf b
x.b<-get("x", environment(f.b))
y.b<-get("y", environment(f.b))
#end
I want to plot the max distance between the two ecdf curves as in the
above given chart
Is that possible and how?
Thanks for your help
PS: this is an amended version of a previous thread (but no reply
followed) that I?ve deleted from Nabble repository because I realised it
was not enough clear (now I hope it?s a little better, sorry for that)